1. Field of the Invention
The present invention relates to a 1-port type surface acoustic wave device including a 1-port surface acoustic wave resonator and a base substrate which are connected together by solder bump bonding.
2. Description of the Related Art
FIGS. 5 through 7 show the construction of a conventional 1-port type surface acoustic wave device consisting of a base substrate and a 1-port surface acoustic wave resonator placed thereon and connected thereto by solder bump bonding. FIG. 5 is a plan view of the 1-port surface acoustic wave resonator; FIG. 6 is a plan view of the base substrate; and FIG. 7 is a sectional view of the 1-port type surface acoustic wave device.
As shown in FIG. 5, this 1-port surface acoustic wave resonator, indicated by numeral 10, includes a surface acoustic wave substrate 11. In the substantially central portion of one main surface of the surface acoustic wave substrate 11, there is provided an IDT electrode 12. Reflector electrodes 13 are provided on either side of the IDT electrode 12. Further, two input/output extraction electrodes 14 extend out from the IDT electrode 12. A round input/output bump electrode 15 is located at the forward end of each extraction electrode 14.
The base substrate, which is indicated by numeral 20, is formed of a ceramic material, such as alumina. As shown in FIG. 6, on one main surface of the base substrate 20, a rectangular-loop-like bonding land 21 is provided for allowing the base substrate to be soldered to a metal cap 30. Further, two round input/output electrode lands 22 are provided for connecting and securing the 1-port surface acoustic wave resonator 10 to the base substrate electrically and mechanically, and two extraction electrodes 23 are respectively connected to the input/output electrode lands 22 and provide a desired electrical connection. On the other main surface of the base substrate 20, input/output terminal electrodes (not shown) are provided and are connected to the extraction electrodes 23 via through-holes 25 or the like.
As shown in FIG. 7, in the conventional 1-port type surface acoustic wave device, the 1-port surface acoustic wave resonator 10 is joined to the base substrate 20 in a face down arrangement. That is, that surface of the 1-port surface acoustic wave resonator 10 on which the electrodes shown in FIG. 5 are disposed is arranged facing downwards and, in this condition, the input/output bump electrodes 15 of the 1-port surface acoustic wave resonator 10 are connected and secured, electrically and mechanically, to the input/output electrode lands 22 of the base substrate 20 via of solder bumps 51. Then, the metal cap 30, one side of which is open, is joined to the bonding land 21 of the base substrate 20 by solder 52, whereby the 1-port surface acoustic wave resonator 10 is sealed in the package defined by the base substrate 20 and the metal cap 30.
As described above, the 1-port surface acoustic wave resonator has two input/output terminals. In the conventional 1-port type surface acoustic wave device, the 1-port surface acoustic wave resonator 10 is joined to the base substrate 20 by solder bump bonding between the two input/output bump electrodes 15 and the two input/output electrode lands 22 of the base substrate 20, which are located at positions corresponding to the input/output bump electrodes 15 so as to provide solder bump bonding at two positions.
Apart from the above-described 1-port type surface acoustic wave device, which is equipped with a 1-port surface acoustic wave resonator, there exists a 2-port type surface acoustic wave device which has a construction similar to that of the 1-port type surface acoustic wave device and which has a 2-port surface acoustic wave resonator with two IDT electrodes joined to a base substrate by solder bump bonding. The 2-port surface acoustic wave resonator has four terminals: two input/output terminals and two grounding terminals. Generally speaking, bump electrodes and electrode lands corresponding to the four terminals are formed on the 2-port surface acoustic wave resonator and the base substrate. The bump electrodes and the electrode lands which are located at positions which correspond to each other are connected together by solder bump bonding.
Thus, the conventional 1-port type surface acoustic wave device has a problem in that, even when it is formed by using a surface acoustic wave resonator and a base substrate which have the same sizes as those of a 2-port type surface acoustic wave device, it is impossible to use the same tools for its production as those used for the production of the 2-port type surface acoustic wave device. For example, the tool used in providing solder bumps on the base substrate and the tool used in effecting solder bump bonding when forming a 1-port type surface acoustic wave device must be different from those used when forming a 2-port type surface acoustic wave device. That is, when producing the above-described 1-port type surface acoustic wave device, it is impossible to use the tools for producing a 2-port type surface acoustic wave device. Thus, it is difficult for the same tools to be used in the production of different types of surface acoustic wave devices. As a result, the administration of the tools is rather difficult, resulting in a high cost in terms of administration and production.
Further, in the conventional 1-port type surface acoustic wave device, the 1-port surface acoustic wave resonator is only joined to the base substrate by two solder bumps, so that the conventional 1-port type surface acoustic wave device exhibits a rather poor impact resistance when, for example, it is dropped.